A wireless communication system provides a user with a communication service by using a radio channel. The wireless communication system includes a user terminal and a plurality of base stations for performing wireless communication. The base stations provide wireless access to terminals located in a geographical area that covers a certain range. The geographical area is called a cell. Therefore, when the terminals move from one place to another, a cell in which the wireless access is provided to each terminal may change. Accordingly, the number of terminals located in each cell also change.
When a serving base station, that is, a base station to which wireless access is provided, changes due to the movement of the terminal, it is called a handover. When the terminal performs the handover, if the base station has buffered data to be transmitted to the terminal, the base station can deliver to a target base station the data to be transmitted to the terminal through a backhaul network, and thus can prevent the data from loss. In order to forward handover data, the base station based on the conventional technique inputs buffered data to a buffer of an uplink scheduler so that the data is transmitted in a competitive manner with respect to uplink data.
However, the following problem may arise when the data which is forwarded due to the handover is input to the buffer of the uplink scheduler. When a plurality of terminals perform the handover, traffic of a terminal which first starts the handover results in a forwarding delay in data of a terminal which starts the handover at a later time, and thus a handover data interruption time increases. As a result, there is a decrease in a service satisfactory level of a user of the terminal which starts the handover at the later time. In addition, since capacity of a backhaul network is limited, an overflow may occur in the buffer of the uplink scheduler, which may lead to a packet loss and a decrease in a data transfer rate.
Accordingly, there is a need for a method for solving the aforementioned problems when data of a terminal which performs a handover is forwarded in a wireless communication system.